1. Field of the Invention
The invention relates to a new and unique varnish formulation derived from vegetable-based (soybean) rather than petroleum-based oils. Ink pigments and other ingredients are added to the varnish which serves as the vehicle for the intaglio inks used in the production of United States currency and other obligations and securities. Intaglio inks are unlike offset and flatbed inks in that they are extremely viscous, high-solid inks and not conducive to use in these other printing processes.
2. Background Discussion
The United States Bureau of Engraving and Printing is the agency responsible, under 31 U.S.C. .sctn.5114, for the production of United States currency, as well as other obligations and securities. The Bureau is by far the largest banknote house in the world. The Bureau produces more currency notes than the seven next largest producers combined.
31 U.S.C. .sctn.5114 requires that currency be manufactured by the intaglio printing process which involves the use of engraved plates. Because the image to be reproduced is engraved below the surface of the printing plate, it is necessary to cover the entire printing plate with ink, forcing the ink into the engraving, and then wipe away all the excess ink remaining upon the surface of the plate. A "distinctive" rag (75% cotton/25% linen) banknote paper is then forced into the engraving by several tons of pressure to lift the inked image from the plate. This "distinctive" paper is adopted by the Secretary of the Treasury, under the provisions of 18 U.S.C .sctn.474a, for the exclusive use of the United States. The mere possession of this paper without proper authority is criminally punishable.
Intaglio ink comprises a varnish, pigments, emulsifiers, extenders, wax, solvents, mineral oil, driers and deionized water.
Nearly eighty percent (80%) of the high-solid intaglio ink applied to the printing plate is wiped away and, except to the extent it can be captured and reconstituted, it becomes a costly waste product. Although not required by law, the Bureau has been disposing of its excess ink in secure landfills, as if the ink were hazardous waste, as a precaution against the future inclusion of the chemically-based varnish or other ingredients in EPA's list of hazardous chemicals. Despite the high cost of this printing process, resulting from the waste of excess ink and the cost of its environmentally safe disposal, the process remains an integral part of currency production because it results in a three dimensional printed image. This image is a primary deterrent to counterfeiting. For these reasons, the use of large scale intaglio printing is predominantly limited to banknote houses.
Until the early 1980s, currency presses utilized a paper-wiping system to remove the currency ink from the printing plates. The inks utilized by the Bureau of Engraving and printing for these paper-wipe presses were manufactured, for the most part, in-house and were not proprietary to any private contractor or the Bureau. However, the Bureau's ink formulas were classified.
The demands for currency production were steadily increasing at this point in time and projected to greatly increase over the next decade. In fact, the Bureau has gone from producing approximately 3 billion notes per year at the outset of the last decade to more than 9 billion notes at the start of this decade. In the early 1980s, the Bureau began to replace its outdated and worn currency presses with new and more technically advanced press equipment. New intaglio press equipment no longer utilized paper-wipe systems, but had adopted new water-wipe or cylinder-wipe systems.
The new wiping system utilizes rubberized rollers (cylinders) to remove the ink from the printing plate. The cylinders are coated with a wiping solution consisting of caustic soda and castor oil which, in conjunction with scrapers (doctor blades), facilitates the removal of the ink. It was soon discovered that the cylinder-wipe system on the new presses necessitated the use of new ink formulation. As a result, the Bureau began to acquire its ink from a private company which considered the formulations for the inks and, in particular, the ink varnishes to be proprietary.
The current process for printing security documents, especially currency, is sheetfed non-heatset intaglio. Sheet fed non-heatset intaglio inks are based on oxidizable resins and alkyds and are very slow drying. Typically, one side of the currency is printed first and after 24-48 hours, the other side is printed. The typical maximum printing speed of such inks is about 75 m/min. U.S. Pat. No. 4,966,628 discloses typical non-heatset sheet fed intaglio inks suitable for printing of security documents.
The term "intaglio printing" refers to a printing process wherein a printing cylinder or printing plate carries the engraved pattern and the engraved recess is filled with printing ink to be transferred to the printing substrate in order to create the document. In this type of printing, typically a rotating engraved cylinder (usually manufactured from steel, nickel or copper and plated with chromium) is supplied with ink by one or more template inking cylinders by which a pattern of inks of different color is transferred to the printing cylinder. Any excess ink on the surface of the cylinder is then wiped off by a rotating wiper cylinder covered by a plastisol, using a dilute aqueous solution of sodium hydroxide and sulfonated castor oil as an emulsifying medium for the wiped-off excess ink. Thereafter, the printing pattern is transferred under a pressure of up to 105 kg/cm.sup.2 to the substrate.
Recently, a heatset intaglio printing ink was developed at the laboratories of the assignee. Such ink is described in U.S. Pat. No. 5,100,934 assigned to the same assignee. The inks described in the '934 patent permitted security documents, especially currency, to be printed by heatset intaglio, thereby resulting in an improved product and in a printing process which permits the obverse of the printed document to be printed an instant after printing the face. However, the inks described in the '934 patent require relatively high heatset temperatures. While such high temperature insure very rapid drying and high throughput rates, the high heatset temperatures also tend to produce undesirable yellowing and/or crinkling of the paper substrate.
A security document intaglio printing ink should meet the following requirements:
(a) correct rheological properties in respect to transfer of the ink to the printing cylinder and transfer therefrom to the substrate; PA1 (b) ability of the excess ink to be easily and quantitatively removed from the non-image areas of the die surface by the wiping cylinder (wipeability); PA1 (c) ease of cleaning the wiping cylinder by means of a cleanser such as dilute aqueous caustic soda solution containing about 1% NaOH and 0.5 % sulfonated castor oil or other surfactants; PA1 (d) stability of the ink on the printing rollers; i.e. control of the evaporation of volatile materials during the printing process to prevent premature drying of the ink on the rollers; PA1 (e) film-forming characteristics allowing handling of the paper carrying printed films of up to 200.mu. thickness immediately after printing; PA1 (f) proper drying properties when printing at speeds of up to 200 m/min. with engravings of up to 200.mu. thickness; PA1 (g) outstanding chemical and mechanical resistance of the printed document pursuant to specifications established by INTERPOL at the 5th International Conference on Currency and Counterfeiting in 1969 and by the U.S. Bureau of Engraving and Printing in BEP 88-214 (TN) .sctn.M5. PA1 (a) chemical resistance to solvents, acids, alkalies, soaps and detergents; PA1 (b) ink film integrity rub test; PA1 (c) crumple test; PA1 (d) laundering test; PA1 (e) soiling test; PA1 (f) humidity and temperature stability; PA1 (g) flexing test; PA1 (h) fade resistance test; and PA1 (i) magnetic properties test.
To be useful as an intaglio ink for currency, the ink on the currency is tested to determine if it passes tests such as the following:
Environmental and worker safety requirements for these inks are also very important. Pursuant to applicable environmental statutory and regulatory requirements placed on Bureau operations, the level of volatile organic compounds (VOCs) in the currency inks were subject to specific limitations. Periodic testing (required by the Bureau's operating permits) of samples of the ink supplied by a private contractor established that the ink was not always within these limitations. Moreover, Bureau employees have complained of noxious odors from some batches of ink, but not others. Employees claimed problems with chemical sensitization and other health problems despite the fact that the material safety data sheets accompanying the ink indicated no toxic materials or other hazards present in the ink. Without access to the formulations of the private contractor-supplied inks, investigation of these problems was greatly hampered.
Moreover, the U.S. House of Representatives Committee on Appropriations, has also requested promoting American agricultural products and reducing dependency on petroleum through the use of soybean oil-based inks in the production of U.S. securities at the Bureau of Engraving and Printing (BEP). In addition, soybean oil is one of our largest agricultural crop by-products and about 20% of the bean being soybean oil. The search for industrial markets such as inks will eventually provide the American farmer with increased markets for his products. The United States is the world's largest producer of soybeans and is a major exporter of the product to other countries. The soybean market is much more stable compared to the price of petroleum: there have been no major drops or upward spikes since soybean oil was developed.
Although changes in the design and appearance of currency are rare, changes in ink formulations have become a relatively common occurrence. As indicated above, changes in the ink formulations were necessitated by new production equipment and processes. The increased focus over the past two decades in the areas of environmental quality and occupational safety have led to regulatory requirements concerning an ever increasing number of materials. Elimination of an ink ingredient in favor of a more environmentally sound or occupationally safe ingredient has resulted in other problems with ink adhesion and print durability.
The Bureau has not always been able to adequately address the above problems through the acquisition of inks from private industry. Due to the unique nature and limited use of intaglio inks, they are not widely manufactured and research development of this ink technology is not broadly available.